This invention relates to a tool for the installation of items that require tensioning and more particularly to a tool for the installation of fasteners such as cable ties.
Cable tie fasteners are commonly installed, for example, by wrapping their straps around groups of articles and then threading the straps through locking heads. The installation is completed by pulling on the free ends of the straps until the articles are securely bundled. To achieve a suitable installation it is desirable to use a tool which grips and tensions the free end of the strap. The free end is then severed in the vicinity of the head when a specified level of tensioning has been reached.
Installation tools in common use contain a trigger actuated mechanism that tensions the strap to a predetermined level and actuates a cutter to sever the strap.
Such tools commonly require the application of a relatively high operating force to the trigger through an appreciable interval. In some cases there is a considerable span between the hand grip of the gun and the trigger. The result is that the tools can be difficult to operate and can cause undue user fatigue.
Another characteristic of existing installation tools is that the cutoff mechanism produces a significant shock effect. At the instant of severing there is pronounced snap which, at high tension levels, can even sting the user. In addition there is the objectionable tendency for the severed end of the strap to be ejected from the tool towards the user. Another objection is the tension level adjusting mechanism is often unreliable and difficult to operate.
Accordingly, it is an object of the invention to reduce the shock effect associated with the severing of items under tension. A related object is to reduce the shock effect associated with the severing of tensioned fasteners. A further related object is to reduce the shock effect associated with the severing of tensioned cable tie straps.
Another object of the invention is to achieve an installation tool in which an item may be tensioned and severed using a reduced amount of trigger force. A related object is to achieve the tensioning and severing of an item using a trigger which has a comparatively short operating span.
A further object of the invention is to provide an accurate and easily adjustable tensioning level for an installation tool.
Still another object is to avoid the objectionable tendency of items that are severed under tension to fly back and strike the operator.
Illustrative installation tools of the prior art are disclosed in U.S. Pat. Nos. 3,735,784; 3,712,346; 3,661,187; 3,433,275; 3,344,815; 3,332,454; 3,284,076; 3,173,456; 3,169,560 (Re. 26,492); 3,168,119; 3,154,114; 2,729,994; 2,882,934; and 2,175,478.